He thanked his running mate, Paul Ryan, who will continue in Congress, and his wife, Ann.

"She would've been a wonderful first lady. She has been that and more to me and our family," Romney said.

The GOP nominee thanked his sons, daughters-in-law and grandchildren, his campaign leaders and his supporters, and said he wished he'd been able to fulfill their hopes on this Election Day.

"I ran for office because I'm concerned about America," he said. "This election is over, but our principles endure."

The mood had changed from hours earlier, when Romney said he was so confident of a win, he had prepared only one speech -- a 1,118-word victory address.

He said then he was "very proud" of the campaign, adding that "no campaign is perfect."

Romney's campaign didn't slow on Election Day. The former Massachusetts governor had embarked on a last-minute push for votes in Ohio and Pennsylvania instead of spending the day in his hometown, as is traditional for candidates.

The two Election Day campaign stops capped a campaign season of upheaval, unconventional moves and late-in-the-game surges that made Tuesday's outcome difficult to predict. Both states' electoral votes went to Obama, CNN projected.

After waking up Tuesday at home in Belmont, Massachusetts, and voting at his local polling place, the campaign charter headed for the heavily contested stretch of middle America known as the Rust Belt. The GOP presidential nominee made two quick, informal stops in Cleveland and Pittsburgh to thank volunteers and help with get-out-the-vote efforts.

Romney and Ryan stopped for a quick lunch at a Wendy's restaurant in Cleveland. Surrounded by cameras, Romney ordered a regular quarter-pound burger without cheese, baked potato with chili while Ryan settled for a No. 1 with iced tea (sweet).

"We figured because Wendy's was invented in Ohio there's no better place to get lunch than at Wendy's, right?" Romney said in a phone call to the restaurant's supervisor, which was caught on camera.

Romney spent time in Ohio almost every day this week, and his campaign said a rising tide of momentum had Pennsylvania in play.

But top advisers, almost all of whom traveled with the candidate as the race came to a close, were immediately confronted with questions about whether Election Day campaigning signaled unease.

A senior Romney adviser told reporters that campaigning on Election Day was the new normal. Both Obama and Sen. John McCain made stops on voting day in 2008, as did George W. Bush and John Kerry in 2004.

But even as polls in Ohio tightened over the last month, often within poll's margins of error, Obama maintained a stubborn lead there. Romney's internal campaign polling showed Obama leading Ohio by five points on Sunday, the final day the campaign polled the state, two GOP sources told CNN.

On Election Day eve, Romney sought to portray victory as Tuesday's likely outcome, and cited the enthusiastic audiences who greeted him in four states as proof.

"If anyone out there that's following American politics wants to know where the energy is, just come right here in this room and you'll see it," he told a crowd of 8,500 in Fairfax, Virginia. "I am looking around to see if we have the Beatles here or something to have brought you but it looks like you came just for the campaign, and I appreciate it."

Romney aides tried to reassure Republican opinion makers in Washington during conference calls on Tuesday, one participant confirmed to CNN. They said the campaign spent more than Obama's during the last week.

But it wasn't enough for him to win Tuesday, despite the cheers and shouts from the crowd in Boston.

"Thank you, and God bless America," Romney said before leaving the podium. "You guys are the best.